Salicylic acid, the active molecule in aspirin and some acne medications, is a hormone in plants that is essential for immunity, but it’s a double-edged sword: Too much can cause autoimmunity and stunt growth. In a new study published April 20 in Nature Communications, University of California, Davis, researchers discovered that plants use a surprising multi-layered system to regulate salicylic acid levels and keep their immune system in check.
Rising salicylic acid levels trigger the production of enzymes that break down the hormone, but in carrying out their job the enzymes are themselves flagged for elimination, which limits how much salicylic acid they can destroy. The findings could be used in agriculture to make crops more resilient to changes in their environment.
“Through this layered control, plants are able to balance immunity with growth, responding quickly to threats while avoiding the cost of prolonged defense,” said senior author Nitzan Shabek, an associate professor of plant biology at UC Davis whose lab combines biochemistry and structural biology to investigate plant signaling. “Our discovery could open the door for innovation in agriculture by enabling new ways to fine-tune crop immunity without compromising growth.”
Uncovering a new layer of control
The first clue came a few years ago, when Shabek’s research group was mapping proteins that interact with the ubiquitin system, the machinery that cells use to recycle proteins. In that study, published in New Phytologist, the team was surprised to spot two salicylic acid-destroying enzymes (DMR6 and DLO1) as potential ubiquitin targets.
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